In the related art, there is a refrigerating air conditioning system in which CO2 is used as a refrigerant, a receiver for storing the refrigerant is provided at an exit of an evaporator or at an entrance of a decompression device, and the amount of refrigerant in the receiver is controlled, so as to control an operating high-pressure of the system to provide a predetermined cooling capability (for example, see Patent Document 1).    Patent Document 1: Japanese Patent Publication No. 7-18602 (P. 1-5, FIG. 2, FIG. 3)